Python list() Function

The list() function in Python is used to create a new list. It can also be used to convert other iterable data types like strings, tuples, or sets into a list.

Syntax

list([iterable])

Parameters:

• iterable (optional) – An iterable object like string, tuple, set, or dictionary.

Returns:

• A new list containing items from the given iterable.

Example 1: Creating an Empty List

my_list = list()
print(my_list)

[]

Example 2: Converting a String to a List

my_list = list("hello")
print(my_list)

['h', 'e', 'l', 'l', 'o']

Example 3: Converting a Tuple to a List

my_list = list((1, 2, 3))
print(my_list)

[1, 2, 3]

Example 4: Converting a Set to a List

my_list = list({10, 20, 30})
print(my_list)

[10, 20, 30]  

Example 5: Converting a Dictionary to a List

my_dict = {'a': 1, 'b': 2}
my_list = list(my_dict)
print(my_list)

['a', 'b']

Note: Only the keys of the dictionary are added to the list.

Use Cases

• Convert data types like tuples or sets to a list for modification
• Split a string into a list of characters
• Convert dictionary keys into a list for iteration

Common Mistakes

• list is not a function call: Forgetting parentheses: my_list = list assigns the function, not a list.
• Non-iterable input: list(5) will throw TypeError because int is not iterable.

Interview Tip

In interviews, the list() function is often used to convert generators or iterators to lists for easier access and manipulation.

Summary

• list() creates a list from an iterable or creates an empty list.
• Commonly used to convert other data types to a list.
• Only iterable objects can be passed.

Practice Problem

Convert the string "Tutorial" into a list of characters, and print it.

word = "Tutorial"
letters = list(word)
print(letters)